Field installable rugged optical terminus

ABSTRACT

A terminus for a fiber optic cable has a ferrule with a fiber stub secured in a channel of the ferrule. The fiber stub has a polished forward end face. The fiber stub extends from a rearward end of the ferrule so that a rearward end face of the fiber stub is rearwardly spaced from the ferrule. An alignment member is axially aligned with the ferrule and has a channel extending between forward and rearward ends of the alignment member. The channel includes a fiber alignment portion in which the rearward end face of the fiber stub is received. The fiber alignment portion is statically configured to receive a forward end face of the filament of the fiber optic cable in opposed relationship to the rearward end face of the fiber stub and axially align the faces to each other.

TECHNICAL FIELD OF THE INVENTION

The technology of the present disclosure relates generally to fiberoptic cables and, more particularly, to a rugged terminus that is fieldinstallable to terminate a fiber optic cable.

BACKGROUND

Military, commercial avionics, and industrial networking equipmentmanufacturers are adopting fiber optic components for communicationapplications. An exemplary communication application is to create anoperative communication link between a control system and a sensor orother data collection device. Fiber optic links are often used toreplace existing electrical (e.g., “copper”) wiring architecturesbecause they provide higher speed, improved electro-magneticinterference (EMI) performance, lower weight, and increased density.Other advantages of fiber optic links include higher data capacity usingmultiple wavelengths and running multiple protocols on the same fiber.As a result of these advantages, system upgrades often may be madewithout replacing the existing fiber optic cable which may run in anarea that is difficult to access.

Most fiber optic products are designed for the telecommunicationsmarket. But these products are generally not rugged enough to withstandthe environmental factors that would adversely affect fiber opticsystems in harsh operating environments where extreme states ofvibration, shock, and temperature may be present.

One component of a fiber optic link that may be ruggedized is theterminus that terminates the fiber optic cable. A common terminus thatis considered rugged enough for harsh environments, such as in off-roadand military vehicles, airplanes, helicopters, spacecraft, etc., is anARINC 801 terminus. An exemplary ARINC 801 terminus 10 is shown incross-section in FIG. 1. An exemplary fiber optic cable that isterminated by the exemplary ARINC 801 terminus is shown in FIG. 2.

In FIG. 2, various layers of the fiber optic cable 12 have been cut awayto show underlying layers. The fiber optic cable 12 includes a fiberoptic filament 14, which is sometimes referred to as a fiber. The fiberoptic filament 14 allows light signals to propagate therein to carry outoptical communications between optical transceivers (not shown) locatedat the respective ends of the fiber optic cable 12. The fiber opticfilament 14 may include a core and a cladding, which are typically madeof glass or plastic. In some fiber optic cables, the filament 14 may becoated with an inner coating layer (not shown in FIG. 2) known as aprimary buffer or simply as a coating. The inner coating layer may bemade from acrylate or polyimide, for example.

The fiber optic filament 14 (and inner coating layer, if present) issurrounded by one or more coating layers, such as the illustrated buffer16. The buffer 16 may be referred to as a secondary buffer. The buffer16 may be made from PTFE, for example. In the illustrated embodiment,the buffer 16 is surrounded by strength members 18, such as aramid yarn.One or more jacketing layers, also referred to as a jacket 20, surroundthe strength members 18. The jacket 20 may be made from PFA, forexample.

One type of fiber optic cable 12 has a loose jacket and a tight buffer.In this type of cable, the cable 12 is constructed so that the jacket 20is able to move along a longitudinal axis of the fiber optic cable 12relative to the buffer 16. This relative movement tends to correspond tomovement and bending of the cable 12 and/or to differing rates ofthermal expansion or contraction among the layers of the cable 12 duringexposure to hot or cold temperatures. The ability of the jacket 20 tomove relative to the buffer 16 give rise to the term “loose jacket”since the jacket 20 is “loose” enough about the buffer 16 to allow forthe movement. Also, in this type of cable, the buffer 16 does not movelongitudinally relative to the filament 14. The inability of the buffer16 to move relative to the filament 14 gives rise to the term “tightbuffer” since the buffer 16 is “tight” about the filament 14 and imposessufficient friction to resist movement. In the case of the loose jacketand a tight buffer fiber optic cable, the buffer 16 and filament 14 movetogether relative to the jacket 20. As used herein, the term “loosejacket” includes “semi-loose jacket,” which is a term used in industryto refer to a cable 12 having a jacket 20 that is less loose than otherloose jacket cables 12.

Another type of fiber optic cable 12 has a tight jacket and a loosebuffer. In this type of cable, the cable 12 is constructed so that thejacket 20 does not move longitudinally relative to the buffer 16. Theinability of the jacket 20 to move relative to the buffer 16 gives riseto the term “tight jacket” since the jacket 20 is “tight” about thebuffer 16 and imposes sufficient friction to resist movement. Also, inthis type of cable, the buffer 16 is able to move along the longitudinalaxis of the fiber optic cable 12 relative to the filament 14. This isachieved by the filament 14 (or primary buffer, if present) having asmaller outside diameter than the inside diameter of the secondarybuffer 16. This relative movement tends to correspond to movement andbending of the cable 12 and/or to differing rates of thermal expansionor contraction among the layers of the cable 12 during exposure to hotor cold temperatures. The ability of the buffer 16 to move relative tothe filament 14 gives rise to the term “loose buffer” since the buffer16 is “loose” enough about the jacket 14 to allow for the movement. Asused herein, the term “loose buffer” includes “semi-loose buffer,” whichis a term used in industry to refer to a cable 12 having a buffer 16that is less loose than other loose buffer cables 12.

One other type of fiber optic cable is a fiber optic cable 12 with atight jacket and a tight buffer. In this type of cable, the cable 12 isconstructed with both the tight jacket and the tight buffer propertiesdescribed above. As such, the jacket 20 does not move longitudinallyrelative to the buffer 16 and the buffer 16 does not move longitudinallyrelative to the filament 14.

One other type of fiber optic cable is a fiber optic cable 12 with aloose jacket and a loose buffer. In this type of cable, the cable 12 isconstructed with both the loose jacket and the loose buffer propertiesdescribed above. As such, the buffer 16 may move relative to both thefilament 14 and the jacket 20.

In each of these fiber optic cable types, if the inner coating layer ispresent, the inner coating layer does not move longitudinally relativeto the filament 14. Thus, the inner coating layer may be consideredtight to the filament 14. In cases where the inner coating layer ispresent and there is a tight buffer 16, each of the buffer 16, the innercoating layer and filament 14 do not longitudinally move relative to oneanother. Hence, the buffer 16 may still be referred to as a tightbuffer. In cases where the inner coating layer is present and there is aloose buffer 16, the inner coating layer and filament 14 do notlongitudinally move relative to one another but the inner coating layerand filament 14 move together relative to the buffer 16. Hence, thebuffer 16 may still be referred to as a loose buffer.

Loose buffer cable arrangements are sometimes referred to as “loosetube” cables.

The relative amount of friction between the layers of the fiber opticcable 12 is typically established by the manner in which the fiber opticcable 12 is manufactured, such as by coextruding layers to be either“tight” with respect to each other or “loose” with respect to eachother. It will be appreciated that a tight jacket may still allow forsome local movement of the buffer 16 with respect to the jacket 20and/or a tight buffer may still allow for some local movement of thefilament 14 with respect to the buffer 16. But movement over relativelylong distances will tend not to occur under normal operating conditionsfor tight configurations, including harsh conditions with high amountsof shock, vibration or temperature variations, such as that found inoff-road and military vehicles, airplanes, helicopters, spacecraft, etc.

Connectors for fiber optic cables have integral dynamic retentionmechanisms, such as a flexible tab or latch that catches on acoordinating feature of a receptacle. A terminus for rugged applicationsmay be distinguished from a connector by a lack of a dynamic retentionmechanism integrated with the terminus. Thus, a terminus is typicallyinstalled in a connector and the connector has a retention mechanism forretaining the terminus. The connector, in turn, may be installed in areceptacle associated with a transceiver and the dynamic retentionmechanism of the connector latches to the receptacle. Some connectorsmay have multiple ports and retention mechanisms for retaining aplurality termini. In the example of an ARINC 801, the retentionmechanism may be resilient metal fingers (not shown) that engage ashoulder on the terminus body (described below). In other arrangements,the terminus is installed in a housing that includes a transceiver andretention components (e.g., resilient fingers) to retain the terminus.

Termini for rugged applications are typically of metal construction andare terminated to fiber optic cables using factory termination. That is,for use in harsh environments, it is typical that the cable 12 isconnected to the terminus (e.g., terminus 10) in a factory setting toensure proper termination. In the case of the terminus 10, the filament14 (optical fiber) is terminated to a ceramic ferrule 22. The ferrule 22has precise inside and outside diameters and concentricity about thefilament 14. A secure connection is made between the filament 14 and theferrule 22 with robust heat curable adhesive. An excess length offilament 14 that extends past the front end of the ferrule 22 is thencleaved, polished, and inspected. The resulting termination hasexcellent optical performance through the passive alignment provided bythe ceramic ferrule 22 and the polish on the fiber end face. This typeof termination also provides excellent mechanical performance by rigidlyfixing the fiber within the ferrule 22, which is a very hard ceramiccomponent capable of withstanding many mating cycles and repeatedmechanical stresses.

The ferrule 22 is held by a ferrule holder 24 which is retained in aterminus body 26. The ferrule holder 24 and ferrule 22 are allowed topiston within the terminus body 26. A spring 28 forwardly biases theferrule holder 24 and ferrule 22. The strength members 18 and jacket 20in the illustrated example are secured to a rearward portion of theterminus body 26 by a crimp sleeve 30 that is crimped about an anchorportion of the terminus body 26. The buffer 16 is supported by theterminus body 26 and the ferrule holder 24. It is typical that thefactory termination of the cable 12 includes bonding the buffer 16 tothe ferrule holder 24 with heat curable adhesive. Together with theother secure connections in the terminus 10, securing the buffer 16 tothe ferrule holder 24 results in the joining of the ferrule 22, fiber(filament 14), ferrule holder 24 and the buffer 16 as a unit that movestogether relative to the terminus body 26. As indicated, the terminusbody 26 has a shoulder 32 against which a latching finger of areceptacle may engage.

Instead of a mechanical crimp connection, some termini employ a bondingcup. A bonding cup is a receptacle for adhesive to flow around thestrength member and jacket to attach the cable to the body of theterminus.

In rugged applications, the retention of the strength member and jacketto the terminus body is often separate from the retention of the fiberand secondary buffer. This allows for relative movement between thefiber and the secondary buffer and allows for relative movement betweenthe fiber and the strength members/jacket. This configuration isreferred to as being “pull-proof” since it prevents forces that areapplied to the jacket from being applied to the ferrule and the fiberend face. Otherwise, these forces could create an air gap between thefiber and an optical element to which the forward end face of the fiberis intended to engage. An air gap will result in loss of communicativeconnection.

Unfortunately, this factory termination process requires hours to curethe adhesive and to cleave, polish and inspect the fiber. The processalso involves numerous pieces of bench top equipment to ensure thetermination is successful. As a result, this process is not well suitedfor field termination of fiber optic cables.

Attempts have been made to fabricate a terminus that is fieldinstallable, but with the benefits of a factory termination. Theresulting products are known as “splice-on” or “pre-terminated”connectors in which a fiber stub is terminated to a ferrule in thefactory. Also, in factory, the fiber stub's forward end is polished andthe rearward end face is precision cleaved and ends either in orimmediately behind the connector. The cleaved end face of thisterminated and polished fiber can then be aligned and coupled to acleaved end face of a fiber during field installation without factoryequipment and processes. This cleaved end face coupling can haveexcellent optical performance when done correctly, contributing onlynegligible loss to the connector or terminus performance.

But there are disadvantages to conventional splice-on and pre-terminatedconnectors when it comes to rugged applications, as will be discussed.Fiber optic connectors in environments with extreme temperatures andmechanical stresses often involve special design features andconsiderations that are not found in connectors used for fiber opticapplications in less harsh environments, such as in-building and datacenter applications. For instance, for rugged connectors, metalconstruction is preferred, along with more temperature resistantmaterials and adhesives. Even the fiber optic cable itself may requiremodifications to function in such an environment. For instance, there isa preference in the avionics industry for loose buffer cableconstruction over tight buffer cable construction, which is moreprevalent in the telecommunications industry. The loose bufferconstruction and ability of the filament 14 to move axially relative tothe buffer 16 mitigates stresses that would otherwise be applieddirectly to the filament 14 by the buffer 16 in a tight bufferconstruction.

Although loose buffer construction may be advantageous along the lengthof the cable itself, it can be problematic within a connector orterminus, especially when exposed to mechanical stresses. For instance,in conventional splice-on and pre-terminated connectors, the secondarybuffer may move relative to the terminated fiber and adhered ferrule.This is undesirable because the secondary buffer supports the fiberradially within the connector or terminus and may lead to breakage ofthe fiber within the connector or terminus.

In splice-on or pre-terminated connectors, index matching gel may beused to fill gaps between the end faces of the fibers. Instant adhesiveor mechanical retention (e.g., a crimp) may be used to secure thejacket, strength members or the secondary buffer to the connector bodyor other member, but the position of the adhesive or mechanicalretention is separated from the joint between the end faces of thefibers. The distance between the retention and the end face is too greatto adequately support the filament for rugged operation. For example,instant adhesives are not fit for cure near the optical end face due tothe index of refraction of the adhesive when cured. Also, mechanicalretention of the fiber itself would introduce a risk of damage duringinstallation. Accordingly, the available retention methods are appliedto the buffer or to a higher layer of the cable structure. In ruggedenvironments, especially in the case of loose buffer cables,conventional splice-on or pre-terminated connectors are not sufficientto ensure reliable operation.

SUMMARY

Disclosed is a terminus for a fiber optic cable. The fiber optic cablemay be field terminated with the terminus and the terminated fiber opticcable may be subsequently used in harsh environments for datacommunications. Therefore, the terminus may be considered afield-installable rugged terminus. The disclosed terminus addresses theissues arising in the prior art. The terminus includes an alignmentmember in which a rearward end face of a fiber stub is aligned with andmated to a forward end face of a fiber of the fiber optic cable. In oneembodiment, the alignment member is attached to or made part of aferrule holder. The alignment member is transparent to one morewavelengths of light, such as visible light and/or UV light used to cureindex matching UV-cure adhesive in the terminus. The fiber and thebuffer of the fiber optic cable are cured to the alignment member. Thebuffer, fiber, alignment member, ferrule and fiber stub may pistontogether in the terminus body. As a result, the terminus recreates thepull-proof mechanical properties of a factory termination for ruggedapplications without requiring a long adhesive cure or the use ofpolishing equipment in the field. Also, the termination of the fiberoptic cable may be completed in minutes rather than hours. Onceterminated, the fiber optic cable with the terminus may be used inrugged environments and is capable of withstanding temperature extremesand repeated mechanical stresses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of a conventional rugged terminus for a fiberoptic cable;

FIG. 2 is a schematic representation of the fiber optic cable;

FIG. 3 is an exploded view of components of the terminus without thefiber optic cable;

FIG. 4 is a perspective view of the terminus;

FIG. 5 is a top view of the terminus;

FIG. 6 is a bottom view of the terminus;

FIG. 7 is a longitudinal cross-section of the terminus;

FIG. 8 is a perspective view of the terminus with the fiber optic cablebefore termination of the fiber optic cable;

FIG. 9 is a perspective view of the terminus with the fiber optic cablefollowing termination of the fiber optic cable;

FIG. 10 is a top view of the terminated fiber optic cable;

FIG. 11 is a top view of the terminated fiber optic cable;

FIG. 12 is a longitudinal cross-section of the terminated fiber opticcable; and

FIGS. 13-15 are views of an alignment member of the terminus in whichinternal structure is shown in broken lines.

DETAILED DESCRIPTION

Embodiments will now be described with reference to the drawings,wherein like reference numerals are used to refer to like elementsthroughout. It will be understood that the figures are not necessarilyto scale. Features that are described and/or illustrated with respect toone embodiment may be used in the same way or in a similar way in one ormore other embodiments and/or in combination with or instead of thefeatures of the other embodiments.

With reference to FIGS. 3 and 4, respectively illustrated are anexploded view of a terminus 100 and a perspective view of the terminus100 in an assembled state prior to termination of a fiber optic cable102 (FIG. 8). With additional reference to FIGS. 5 and 6, illustratedare a top view of the terminus 100 and a bottom view of the terminus100. In addition, a cross-section taken along the longitudinal axis ofthe terminus 100 is shown in FIG. 7.

The terminus 100 of the illustrated embodiment includes a ferrule 104, aferrule holder 106, a fiber stub 108, a buffer segment 110, a filamentalignment member 112, a spring 114, and a terminus body 116. The ferrule104 may be made from ceramic in the conventional manner. The ferruleholder 106 and terminus body 116 may be made from metal, but othermaterials (e.g., plastic such as acrylic or polyetherimide) are possibleif non-conductive properties are desired. The filament alignment member112 may be made from glass or plastic, and is preferably transparent towavelengths of light used to cure UV adhesive in the terminus 100, aswill be described.

The terminus 100 of the illustrated embodiment is constructed to becompatible with ARINC 801 receptacles and to have ruggedcharacteristics, such as being “pull proof” and insensitive totemperature changes, mechanical shock and vibration. Aspects of thedisclosed terminus 100 may be employed in other form factor termini.

Together, the fiber stub 108 and the buffer segment 110 are a bufferedfiber stub 111. It will be understood, that the terminus 100 may havefewer components or may have additional components. As used herein, theterms “forward” and “rearward” refer to directions along a longitudinalaxis of the terminus 100, with forward being in the direction of a frontface 118 of the fiber stub 108 from a central portion of the fiber stub108. The front face 118 is located at a forward end 120 of the ferrule104 and is intended to optically connect with an optical component (notshown) into which the terminus 100 is eventually connected (e.g., atransceiver or passive optical device). Similarly, rearward is in thedirection of a rear face 122 of the fiber stub 108 from a centralportion of the fiber stub 108.

In a preferred embodiment, the terminus 100 is assembled using factorytermination techniques. Steps involved in this process will bedescribed, but it will be understood that additional steps may be added,one or more steps may be omitted, and some steps may be carried outconcurrently or in an overlapping manner.

A rearward end 124 of the ferrule 104 may be press fit into acoordinating central bore 126 of the ferrule holder 106. In addition toor instead of a press fit, the ferrule 104 may be secured in the centralbore 126 with adhesive. The central bore 126 of the ferrule holder 106may have a stepped inner diameter to accommodate the ferrule 104 at aforward end of the ferrule holder 106 and to accommodate and radiallysupport the buffer segment 110 at a rearward end of the ferrule holder106.

The buffered fiber stub 111 starts as a length of buffered fiber, whichmay be considered a fiber optic cable having at least a filament thatbecomes the fiber stub 108 and a secondary buffer that becomes thebuffer segment 110. A primary buffer may be present and, if present, isstripped away from the filament. Strength members and a jacket also maybe present and, if present, are removed during the assembly process.Thus, it is more likely that manufacturers of the terminus 100 will optto use an unjacketed cable to make the buffered fiber stub 111. Thebuffered fiber may be of tight buffer configuration. In anotherembodiment, the buffered fiber may be of loose buffer configuration. Ineither case, adhesive will further secure the buffer segment 110 to thefiber stub 108 and other components of the terminus 100 (e.g., theferrule holder 106 and/or the alignment member 112) to fix the axialposition of the buffer segment 110 relative to the fiber stub 108.

The buffered fiber is stripped to expose fiber forward of the buffersegment 110. The exposed fiber is inserted through the central channelof the ferrule 104 in the forward direction so as to extend beyond thefront end 120 of the ferrule 104. The fiber is secured to the ferrule104 with, for example, heat curable adhesive. Once cured, excess fiberforward of the ferrule 104 may be removed by cleaving. Then, the fiberis polished, which also removes excess adhesive at the forward end 120of the ferrule 104. This forms the forward end 118 of the fiber stub 108at the forward end 120 of the ferrule 104.

The buffered fiber is stripped to establish the buffer segment 110 andexpose fiber rearward of the buffer segment 110. If a primary buffer ispresent, the primary buffer may be stripped rearward of the buffersegment 110. In another embodiment, the primary buffer may remainunstripped rearward of the buffer segment 110. The remaining bufferafter stripping forms the buffer segment 110, which is of a definedlength. The exposed fiber (and primary buffer, if present andunstripped) is precision cleaved to establish the rear face 122 of thefiber stub 108. The fiber is cleaved so that the rear face 122 isultimately located in a precision fiber alignment section of thefilament alignment member 112, as will be described.

The assembled ferrule 104, ferrule holder 106 and fiber stub 108 may beattached to the alignment member 112. For this purpose, a rearwardportion of the ferrule holder 106 may be press fit into a coordinatingcentral channel 128 of the alignment member 112. In addition to orinstead of a press fit, the ferrule holder 106 may be secured in thecentral channel 128 with adhesive. A forward portion of the centralchannel 128 of the alignment member 112 may have a stepped innerdiameter to accommodate the ferrule holder 106 and accommodate andradially support a rearward portion of the buffer segment 110 thatextends rearward from the ferrule holder 106.

Prior to insertion of the assembled ferrule 104, ferrule holder 106 andfiber stub 108 into the alignment member 112, UV-curable adhesive thatis index-matched (when cured) to the fiber stub 108 may be introducedinto the alignment member 112, such as with a syringe. The UV-curableadhesive may be introduced, for example, into V-shape passage segment164 (FIG. 14, described below) and forward buffer pocket 160 (FIG. 14,described below). The UV-curable adhesive may be used to bond the fiberstub 108 to the alignment member 112 and bond the buffer 110 to thealignment member 112. The UV-curable adhesive may be cured at this stageor left uncured. If left uncured, the UV-curable adhesive may be curedat the time of termination of the fiber optic cable 102. It may beadvantageous to cure the UV-curable adhesive at the time of terminationof the fiber optic cable 102 so as not to establish cured adhesive onthe rear face 122 of the fiber stub 108 prior to termination of thefiber optic cable 102. Referring to prior steps, the heat curableadhesive used to bond the fiber stub 108 to the ferrule 104 also may beused to bond the buffer 110 to the rearward end 124 of the ferrule 104and/or bond the buffer 110 to the ferrule holder 106.

In one embodiment, the ferrule holder 106 may be omitted and the ferrule104 with buffered fiber stub 111 may be connected directly to thealignment member 112. In this embodiment, the forward portion of thecentral channel 128 may be reconfigured to directly accept the ferrule104 and buffer segment 110.

The spring 114 may be placed around the alignment member 112 until aforward end of the spring 114 engages a shoulder 130 formed on theexterior sidewall of the alignment member 112. The assembled spring 114,alignment member 112, fiber stub 108, ferrule holder 106 and ferrule 104may be inserted into an interior passage 132 of the terminus body 116until a rearward end of the spring 114 engages a shoulder 134 in theinterior passage 132. An alignment key 135 that extends radially fromthe exterior sidewall of the alignment member 112 radially extends fromthe terminus body 116 though a slot 136 in the sidewall of the terminusbody 116. The alignment key 135 coordinates with an alignment groove orslot in a receptacle that receives the terminus 100. In one embodiment,the alignment key is integral with the alignment member 112, such asbeing secured to the alignment member 112 or of monolithic constructionwith the alignment member 112. In another embodiment, the alignment key135 is integral with the ferrule holder 106.

A forward end 138 of the terminus body 116 is swaged inward to act as aforward travel stop to the forward end of the alignment member 112. Thislimits forward movement of the alignment member 112 relative to theterminus body 116 and, similarly, limits rearward movement of theterminus body 116 relative to the alignment member 112. By way of theirconnection to the alignment member 12, the swaged forward end of thealignment member 112 also serves to limit travel of the ferrule holder106, the ferrule 104, and the front face 118 of the fiber stub 108. Theamount of swaging is controlled so that the forward end 138 does notinterfere with forward movement of the terminus body 116 over theferrule holder 106 when the terminus 100 is installed in a coordinatingreceptacle. More specifically, the spring 114 forwardly biases thealignment member 112, connected ferrule holder 106 and ferrule 104, andthe front face 118 of the fiber stub 108 relative to the terminus body116. When the terminus 100 is installed in a connector or receptacle,forward force on the terminus body 116 may cause the spring 114 tocompress and the terminus body 116 to move forward relative to thealignment member 112, connected ferrule holder 106 and ferrule 104, andthe front face 118 of the fiber stub 108. The slot 136 extendslongitudinally so that the alignment key 135 does not limit thisrelative movement of components.

With further reference to FIGS. 8-12 termination of the fiber opticcable 102 with the terminus 100 will be described. FIG. 8 shows thecable 102 and terminus 100 during the termination process. FIGS. 9, 10,11 and 12 respectively show a perspective view, a top view, a bottomview and a cross section of the terminated cable 102.

As shown in FIG. 8, the cable 102 cable 102 is prepared for termination.The cable 102 cable 102 may be constructed in the manner described inconnection with FIG. 2.

Alternatively, the cable 102 may be a buffered fiber without strengthmembers and/or without a jacket. In one embodiment, the cable 102 has aloose buffer. If a jacket is present, the cable 102 may have either atight jacket or a loose jacket. This type of cable is preferred bymanufacturers of aircraft and other products that experience harshconditions and require the use of rugged components for fiber opticconnections. It will be understood, however, that the cable 102 may betight buffer construction.

It is contemplated that preparation of the cable 102 for termination andcompleting the termination on the prepared cable may be completed by atrained technician in about five minutes or less. Of course, aspects ofthe terminus 100 and/or the termination process may be used insituations where preparation of the cable 102 for termination andcompleting the termination takes longer than five minutes.

Preparing the cable 102 may include sliding a crimp sleeve 140 over ajacket 142, stripping the jacket 142 to expose strength members 144,stripping the strength members 144 to expose a buffer 146, and strippingthe buffer 146 to expose a filament 148. If the fiber stub 108 rearwardof the buffer segment 110 includes a primary buffer, it is preferredthat the cable 102 include a primary buffer that is not stripped fromthe filament 148. Alternatively, if a primary buffer is present, theprimary buffer also may be stripped. Other cables 102 may not include aprimary buffer. The filament 148 (and primary buffer, if present and notstripped) is precision cleaved to establish the front face 150 of thefilament 148.

With additional reference to FIGS. 13-15, additional aspects of thefilament alignment member 112 will be described. FIGS. 13, 14 and 15respectively are a perspective view, a side view and a forward end viewof the alignment member 112. Although the alignment member 112 may beclear (e.g., transmissive of visible light), internal structure is shownin broken lines to aid in illustration. The cross-sectional views ofFIGS. 7 and 12 also may be referenced to understand the internalstructure.

In general, the alignment member 112 is a tube-like structure having aforward end 152 and a rearward end 154 with the central passage 128extending between the two ends 152, 154. An exterior wall 156 has adiameter that is enlarged forward the shoulder relative to the exteriorwall 156 rearward of the shoulder 130, thus establishing the shoulder130.

The alignment key 135 radially extends from the enlarged portion of theexterior wall 156. Although some features of the alignment member 112are described as circular or as having circular characteristics, it willbe understood that other cross-sectional shapes are possible.

The central passage 128 varies in cross-sectional area and shape along alength of the alignment member 112. The various features of the centralpassage 128 will be described starting at the forward end 152 andproceeding rearward toward the rearward end 154. Adjacent the forwardend 152, the passage 128 forms a cylindrical pocket 158 that is sized toaccommodate the rearward portion of the ferrule holder 106. Rearward ofthe pocket 158 is a forward buffer pocket 160 that is sized toaccommodate and radially support the buffer segment 110. Rearward of theforward buffer pocket 160, the central passage 128 defines a taper 162that assists in guiding the rear face 122 of the fiber stub 108 intorearward portions of the central passage 128 that have a smallercross-sectional area than the buffer pocket 160. For instance, thenarrow rearward end of the taper 162 leads to a V-shaped passage segment164. The V-shape passage segment 164 supports the fiber stub 108 andassists to guide the fiber stub 108 into a fiber alignment section 166located rearward of the V-shaped passage segment 164. The V-shapepassage segment 164 may have other shapes, including circular. In oneembodiment, the fiber alignment section 166 may be considered acapillary tube.

The fiber alignment section 166 may be circular in cross section andhave a diameter that is the same as or slightly larger than a diameterof the fiber stub 108 and the filament 148. If the fiber stub 108 andfilament 148 include respective unstripped buffers, the fiber alignmentsection 166 may have a diameter that is the same as or slightly largerthan a diameter of the fiber stub 108 with primary buffer and thefilament 148 with primary buffer. In that regard, if the primary buffersare present, they will be respectively considered part of the fiber stub108 and the filament 148. With or without the buffers, the fiber stub108 and the filament 148 are considered to be directly and radiallysupported by the respective segments 164 and 170 of the alignment member112 and by the fiber alignment section 166 of the alignment member 112.

The rearward end face 122 of the fiber stub 108 optically mates with theforward end face 150 of the filament 148 of the fiber optic cable 102 inthe fiber alignment section 166. The size of the fiber alignment section166 facilitates radial alignment of the end faces 122, 150. The endfaces 122, 150 may come into physical contact with one another toestablish the optical mating of the fiber stub 108 and the filament 148.It is also possible that a small amount of UV-curable adhesive islocated between the end faces 122, 150. Since the UV-curable adhesive isindex matched to the fiber stub 108 and filament 148 when cured, thepresence of this UV-curable adhesive may be acceptable to establish theoptical mating of the fiber stub 108 and the filament 148.

Radially adjacent the V-shape passage segment 164 may be a semi-circularor other shaped pocket 168. The pocket 168 facilitates manufacture ofthe smaller features of the central passage 128, such as the V-shapepassage segment 164 and the fiber alignment section 166. In addition,the pocket 168 may accommodate excess UV-curable adhesive so as tofacilitate flow of the UV-curable adhesive around the fiber stub 108 andthe rearward end of the buffer segment 110. The pocket 168 also mayserve as a volume to absorb air bubbles present in the UV-curableadhesive in the central passage 128 or introduced during assembly of theterminus 100. A forward end of the pocket 168 may open to the taper 162.

The fiber alignment section 166 leads to another V-shaped passagesegment 170. The

V-shape passage segment 170 supports the filament 148 and assists toguide the filament 148 into the fiber alignment section 166 locatedforward of the V-shaped passage segment 170. The V-shape passage segment170 may have other shapes, including circular.

Radially adjacent the V-shape passage segment 170 may be a semi-circularor other shaped pocket 172. The pocket 172 facilitates manufacture ofthe smaller features of the central passage 128, such as the V-shapepassage segment 170 and the fiber alignment section 166. In addition,the pocket 172 may accommodate excess UV-curable adhesive to facilitateflow of the UV-curable adhesive around the filament 148 and the buffer146 of the cable 102. The pocket 172 also may serve as a volume toabsorb air bubbles present in the UV-curable adhesive in the centralpassage 128 or introduced during termination of the cable 102. TheV-shaped passage segment 170 and pocket 172 may open to a taper 174. Thetaper 174 assists in guiding the front face 150 of the filament 148 intoforward portions of the central passage 128.

Rearward of the taper 174 is a rearward buffer pocket 176 that is sizedto accommodate and radially support the buffer 146.

The alignment member 112 may be considered a static body. That is, thealignment member 112 does not change shape during termination and doesnot have parts that move relative to one another to accomplishtermination. Thus, according to one embodiment, the fiber alignmentportion 166 of the channel 128, and other portions of the channel 128,are statically configured.

Continuing with the description of the termination process, UV-curableadhesive that is index-matched (when cured) to the filament 148 and thefiber stub 108 may be introduced into the rearward portion of thecentral passage 128 of the alignment member 112, such as with a syringe.The UV-curable adhesive may be introduced, for example, into the V-shapepassage segment 170 and the rearward buffer pocket 176. In oneembodiment, this UV-curable adhesive is introduced in the field as partof the termination process. In another embodiment, this UV-curableadhesive is introduced in the factory as part of manufacture of theterminus 100.

Once the cable 102 is prepared and the UV-curable adhesive is in place,the cable 102 is inserted into the terminus 100. The cable 102 isadvanced so that the filament 148 enters the fiber alignment section166. Preferably, the forward face 150 of the filament 148 contacts therearward face 122 of the fiber stub 108. Additionally, the buffer 146enters the rearward buffer pocket 176 of the alignment member 112. Thestrength members 144 slide over (radially outward from) a forward crimpanchor portion 178 of the terminus body 116. Similarly, the strengthmembers 144 and jacket 142 slide over (radially outward from) a rearwardcrimp anchor portion 180 of the terminus body 116.

At this point the components may be held together in the above-describedconfiguration with a positioning tool (not shown). Next, the UV-curableadhesive is cured by illuminating the UV-curable adhesive with UV light(schematically illustrated by arrows 182 in FIG. 12) emitted by a UVlight source (not shown). The UV light source may be part of thepositioning tool. The UV light may be introduced into the terminus body116 through the slot 136. The terminus body 116 may include one or moreother windows for UV light to enter the terminus body 116. For example,in the illustrated embodiment, the terminus body 116 has an elongatedwindow 184 located adjacent the spring 114 and alignment member 112. UVlight entering the window 184 and the slot 136 may pass between thecoils of the spring 116 and become incident on the alignment member 112.As indicated, the alignment member 112 is transparent to the UV light.Therefore, the UV light will pass through the alignment member 112 andbecome incident on the UV-curable adhesive. In the presence of the UVlight, the UV curable adhesive will cure and establish a bond betweenthe alignment member 112 and each of the buffer 146, the filament 148,the rearward portion of the fiber stub 108, and the buffer segment 110.This mechanically joins the alignment member 112 and each of the buffer146, the filament 148, the rearward portion of the fiber stub 108, andthe buffer segment 110 with the ferrule holder 106, ferrule 104 andforward face 118 of the fiber stub 108 so that they all move togetherrelative to the terminus body 116.

Since the terminus 100 effectively includes a splice established betweenthe end faces 122, 150, the terminus 100 may be referred to as a“pre-terminated terminus.” But, the terminus 100 has similar ruggedizemechanically properties to the termination of the fiber 12 by theterminus 10 of FIG. 1. In one embodiment, no index matching (IM) gel isused in the terminus 100.

To complete the termination, the crimp sleeve 140 may be slid forwardover the crimp anchor portions 178, 180 of the terminus body 116. Thecrimp sleeve 140 then may be crimped into place to trap the strengthmembers 144 and jacket 142 between the terminus body 116 and the crimpsleeve 140.

Additional aspects of the disclosure will be understood from theappended claims, which form part of this specification.

1. A terminus for a fiber optic cable that has a filament surrounded bya buffer, comprising: a ferrule having a forward end, a rearward end,and a channel extending between the forward and rearward ends; a fiberstub secured in the channel of the ferrule and the fiber stub having apolished forward end face at the forward end of the ferrule and arearward end face, the fiber stub extending from the rearward end of theferrule so that the rearward end face is rearwardly spaced from therearward end of the ferrule; an alignment member axially aligned withthe ferrule and having a forward end, a rearward end and a channelextending between the forward and rearward ends, the channel including afiber alignment portion in which the rearward end face of the fiber stubis received, the fiber alignment portion statically configured toreceive a forward end face of the filament in opposed relationship tothe rearward end face of the fiber stub and axially align the forwardend face of the filament with the rearward end face of the fiber stub;and a terminus body surrounding the alignment member.
 2. The terminus ofclaim 1, wherein the alignment member is forwardly biased in theterminus body by a spring.
 3. The terminus of claim 1, wherein theterminus body has one or more openings through which radiation ispassable for curing adhesive that, following curing of the adhesive,secures the fiber stub to the alignment member forward of the rearwardend face of the fiber stub.
 4. The terminus of claim 1, wherein theterminus is configured to establish a pull-proof connection to the fiberoptic cable and the fiber optic cable is of loose buffer configuration.5. The terminus of claim 1, further comprising a buffer segmentsurrounding the fiber stub, the buffer segment rearward of the rearwardend of the ferrule and a rearward end of the buffer segment locatedforward of the rearward end face of the fiber stub, the buffer segmentradially supporting the fiber stub.
 6. The terminus of claim 5, whereinthe buffer segment is at least partially received in and radiallysupported by a forward buffer pocket of the channel of the alignmentmember.
 7. The terminus of claim 6, further comprising adhesive that,following curing, secures the buffer segment to the forward bufferpocket of the channel of the alignment member.
 8. The terminus of claim1, wherein the ferrule is secured at the rearward end of the ferrule tothe alignment member.
 9. The terminus of claim 1, wherein the ferrule issecured at the rearward end of the ferrule to a ferrule holder, and theferrule holder is secured to the alignment member at the forward end ofthe alignment member.
 10. The terminus of claim 9, further comprising abuffer segment surrounding the fiber stub rearward of the rearward endof the ferrule, at least a portion of the buffer segment radiallysupported by the ferrule holder.
 11. The terminus of claim 10, whereinthe buffer segment is at least partially received in and radiallysupported by a forward buffer pocket of the channel of the alignmentmember
 12. The terminus of claim 1, wherein the alignment memberintegrally includes a receptacle alignment key radially extending froman exterior side wall of the alignment member and through an opening inthe terminus body.
 13. The terminus of claim 1, wherein the alignmentmember is transmissive of UV radiation.
 14. The terminus of claim 1,wherein the alignment member includes a rearward buffer pocket rearwardend of the fiber alignment portion, the rearward buffer pocketconfigured to receive and radially support a portion of the buffer ofthe fiber optic cable.
 15. The terminus of claim 1, wherein forward ofthe fiber alignment portion of the channel of the alignment member, thechannel including a section configured to directly and radially supportthe fiber stub and radially align the fiber stub with the fiberalignment portion.
 16. The terminus of claim 15, wherein rearward of thefiber alignment portion of the channel of the alignment member, thechannel including a section configured to directly and radially supportthe filament of the fiber optic cable and radially align the filamentwith the fiber alignment portion.
 17. The terminus of claim 16, whereinthe channel includes a first pocket radially adjacent and fluidlycoupled to the section configured to directly and radially support thefiber stub and a second pocket radially adjacent and fluidly coupled tothe section configured to directly and radially support the filament.18. A fiber optic cable assembly, comprising: the terminus of claim 1;and a fiber optic cable having a filament surrounded by a buffer, thefiber optic cable terminated by the terminus, wherein a portion of thefilament is located in the channel of the alignment member and a forwardend face of the filament is in operative optical connection with therearward end face of the fiber stub in the fiber alignment portion ofthe alignment member.
 19. The fiber optic cable assembly of claim 18,wherein the buffer of the fiber optic cable is secured in the channel ofthe alignment member.
 20. The fiber optic cable assembly of claim 19,wherein the buffer of the fiber optic cable is secured to the alignmentmember with cured UV adhesive
 21. The fiber optic cable assembly ofclaim 18, wherein the filament is secured to the alignment member withcured UV adhesive.
 22. The fiber optic cable assembly of claim 18,wherein the fiber optic cable further includes a jacket and strengthmembers surrounding the buffer and the fiber optic cable assemblyfurther comprises a crimp sleeve, the crimp sleeve trapping the jacketand strength members between the crimp sleeve and an anchor portion ofthe terminus body.
 23. The fiber optic cable assembly of claim 18,wherein the fiber optic cable is of loose buffer configuration.
 24. Amethod of terminating a fiber optic cable, the fiber optic cable havinga filament surrounded by a buffer, strength members surrounding thebuffer and a jacket surrounding the strength members, the methodcomprising: providing a terminus having an alignment member having aforward end, a rearward end and channel extending between the rearwardand forward ends, the channel comprising a fiber alignment portioncontaining a rearward end face of a fiber stub of the terminus, theterminus further having a ferrule coupled to the alignment member, aforward portion of the fiber stub secured in the ferrule and a forwardend face of the fiber stub at a forward end of the ferrule; preparingthe fiber optic cable including stripping the jacket, strength memberand buffer, and cleaving the filament to establish a forward end face ofthe filament; inserting the filament into the alignment portion of thechannel of the alignment member so that the forward end face makesoperative optical connection with the rear end face of the fiber stub inthe fiber alignment portion; and securing the filament and the buffer ofthe fiber optic cable to the alignment member.
 25. The method ofterminating a fiber optic cable of claim 24, wherein the securing of thefilament and the buffer of the fiber optic cable to the alignment memberincludes curing UV adhesive in the channel of the alignment member withUV radiation.
 26. The method of terminating a fiber optic cable of claim25, wherein the UV radiation enters the terminus through one or moreopenings of a terminus body that surrounds the alignment member.
 27. Aterminus for a fiber optic cable that has a filament surrounded by abuffer, wherein a forward portion of the filament has a forward endface, comprising: a ferrule having a forward end, a rearward end, and aferrule channel extending between the forward and rearward ends; a fiberstub secured in the ferrule channel and the fiber stub having a polishedforward end face at the forward end of the ferrule and a rearward endface, the fiber stub extending from the rearward end of the ferrule sothat the rearward end face is rearwardly spaced from the rearward end ofthe ferrule; an alignment member axially aligned with the ferrule andhaving a forward end, a rearward end and an alignment member channelextending between the forward and rearward ends, the fiber stubextending into the alignment member channel so that a rearward part ofthe fiber stub including the rearward end face is located in thealignment member channel, the alignment member channel configured toreceive the forward portion of the filament including the forward endface of the filament and a forward portion of the buffer of the fiberoptic cable, the forward portion of the filament, the forward portion ofthe buffer and the rearward portion of the fiber stub bondable to aninterior wall of the alignment member that forms the alignment memberchannel; and a terminus body surrounding the alignment member.
 28. Theterminus of claim 27, further comprising curable adhesive forestablishing bonds between the interior wall of the alignment member andthe forward portion of the filament, the forward portion of the bufferand the rearward portion of the fiber stub.
 29. The terminus of claim28, wherein the curable adhesive is UV curable adhesive.
 30. Theterminus of claim 29, wherein the alignment member is transmissive of UVradiation.
 31. The terminus of claim 28, wherein the terminus body hasone or more openings through which radiation is passable for curing theadhesive.
 32. The terminus of claim 27, further comprising a buffersegment surrounding the fiber stub, the buffer segment rearward of therearward end of the ferrule and a rearward end of the buffer segmentlocated forward of the rearward end face of the fiber stub, the buffersegment radially supporting the fiber stub and a portion of the buffersegment located in and bondable to the alignment member channel.